that the feed line is at right angles to the antenna. See figure 82.

Figure 81. Doublet antenna sag.

SAG

APPROXIMATE SIGNAL LOSS

20

0 db

30

-1 db

40

-2.5 db

50

-5 db

60

-16 db

70

-24 db

80

-25+ db

At angles of 20 to 80 from the

horizontal, signal loss can be

expected.

Keep

antenna

as

horizontal as possible.

Figure 82. Doublet feed

APPROXIMATE INCLINATION

line problems.

ANGLE LOSS

ANGLE

LOSS

0 - 40

0 db

50

-1 db

60

-5 db

70 - 80

No statistics

At angles of 45 to 60 from a

very poor

perpendicular

plane

to

the

doublet, up to 5 db antenna gain

can be lost. Keep feed line as

perpendicular

from

antenna

toward earth as possible.

c.

The disadvantage of the doublet is its narrow operating

range.

See figures 83 and 84.